Antenna



April 5, 1938. y c. w. HANSLI. ET AL 2,113,136

ANTENNA y 4 Filed Feb. 3. 1936 TRANS.

L/NE

HIGH FREQUENCY AFPA KAN/S INVENTOR. NlLS E. LINDENBLAD E' LARENCEW,HANSELL ATTORNEY.

Patented Apr. 5, 1938 ANTENNA Clarence W. Hansell, Port Jeerson, andNils E. Lindenblad, Rocky Point, N. Y., assignors to Radio Corporationoi' America, a corporation of Delaware Application February s,- isss,sei-n1 No. 62,0111

l5 Claims. (Cl. 250-33) ing directivity in planes other than thevertical l This invention relates to antennas.

A primary object is to enable th transmission of short radio waves withconsiderable vertical directivity and with uniform and maximum radiationin the horizontal plane.

-vA further object is to provide an antenna suitable for use on ultrahigh frequencies which has a broad frequency response curve whereby itwill radiate the modulation sidebands of television, facsimile and otherprogram services.

Another object is to provide a mechanically simple antenna structure ofpleasing appearance suitable for use on the tops of high buildings andtowers.

A further object is to provide a simple mechanical antenna arrangementfor use with ultra high frequencies which gives the equivalent of aseries of dipoles energized in the same phase with respect to oneanother.

These and other objects of the invention which may appear from a readingof the speciilcation are achieved by providing an antenna in the form ofa tube having alternately arranged radiating sections each a half wavelong at the operating frequency and energized such that the currentsflowing therein are in the same direction, whereby cophasal energizationis eiected. The radiation from an intermediate section is suppressed bymeans of a sleeve also a half wave length long surrounding theintermediate section. The sleeve may be either insulatingly positionedwith respect to or fastened metallically at its midpoint to the antennatube and is connected to ground by means of a lead a multiple of a haltwave long extending within the tube from ground to the end of the sleevenearest the high frequency apparatus.

The diameter of the antenna tube is selected to give a desired Width offrequency response curve and is based upon an appreciation of the factthat the width of the curve is increased simultaneously with an increasein diameter of the tube.

A ature of the invention is the adjustable sleeve at the extreme end ofthe antenna tube for obtaining proper adjustment of the length of theantenna.

Advantages of the invention are that the antenna (1) possessesmoderately great vertical directivity but no horizontal directivity`whenerected vertically; (2) is simple to construct; (3) is rigid in.construction; and (4) is easily adapted for use on the top of a highbuilding.

In the accompanying drawing, Figs. 1 and 2 illustrate the invention asapplied to two diilerent lengths of antennas mounted vertically on thetop of abuilding. It will be appreciated, of course, that the antennamay also be positioned horizontally or at any desired angle forobtainplane.

The antenna of Fig. 1 comprises, essentially, a single rod l equal toseven-quarters the length of the communication wave, set one-quarter ofa wavelength more or less into the top of a building. The portion of theantenna above the roof top consists of two half wavelength radiatingportions 2, 2 separated by an eective non-radiating portion 3 from whichradiation is suppressed by a surrounding sleeve 4 also equal to a halfwave-length. Sleeve 4 is grounded to the roof top by a half wavelengthconnection I4 which connects with the sleeve at its lower end andextends inside the tubular antenna, as shown. Connection I4 may connectto the inside or outside of sleeve 4. The lowest quarter wavelengthsection is prevented from radiating by having it sunk into the roof ofthe building. The antenna is energized by high -frequency apparatus,shown conventionally in box form, through transmission line TL whichconnects with antenna l at a tapping point which is adjustable to matchthe impedance of the line TL. In this manner standing waves are set upalong the antenna, and the voltage which is eilective in producingradiation is asindicated in dotted lines on the sections 2, 2.

Sleeve 4 may be insulatingly positioned, or can be fastened metallicallyat its mid-point to the antenna tube 2. If desired, `sleeve 4 may begrounded at its upper end, in which case connection I4 should be an evenmultiple of half the length of the operating wave.

An adjustable sleeve 5 aids in adjusting the length of antenna l. Inorder to broaden the frequency response curve of the antenna so that itmay radiate the modulation sidebands, its diameter is made quite large,herein shown as one-fifteenth the wavelength.

The system of Fig. 2 is similar to that of Fig. 1 except that theantenna is of greater length. In Fig. 2 there are shown three radiatingsections, each one-half wave-length separated from one another by halfwavelength non-radiating sections in the same manner as shown in Fig. 1.In this case the uppermost lsleeve 4' is grounded to the roof top by aconductor equal to three half wavelengths. Instead of such a groundingarrangement for sleeve 4', the lower end of the upper sleeve 4' can beconnected to the upper end of the lower sleeve 4. It will thus beapparent that if the antenna is lengthened, each sleeve may be connectedto ground over a connection equal to an odd multiple of a halfwavelength. Fig. 2 also diiers from Fig. 1 by showing another way ofcoupling the transmission line to the antenna; instead of the directcoupling of Fig. 1, inductive coupling is used, both types of couplingbeing, of course, interchangeable.

It will be understood, of course, that the invention is not limited tothe precise arrangement shown in the figures, since variousmodifications may be made without departing from the spirit and scopethereof. For example, the antennas of Figs. 1 and 2 may be extendedsymmetrically from a center so as to form a structure equivalent to twoantennas end to end, somewhat like an extended dipole antenna. Also,various arrays of antennas may be used to obtain additional directivity,It should also be understood that the expression sleeve is notnecessarily limited to a continuous, solid element but also includes aplurality oi? closely spaced, interconnected wires in the form oi' ascreen and having the general configuration of a cylinder.

What is claimed is:

1. An antenna comprising -two half wavelength radiating sectionsseparated by another half wavelength section, and a sleeve one-halfwavelength long surrounding said last section for preventing radiationtherefrom, the ends of said sleeve on both sides of its center beinginsulated from said last section, and a connection grounding saidsleeve.

2. An antenna comprising a straight rod having high frequency apparatusconnected to one end thereof, alternate half wave sections of which, asmeasured from the free end, radiate, means for preventing radiation fromeach half wave section located between radiating sections comprising asleeve surrounding said section, the ends of said sleeve beinginsulatingly positioned from said antenna, and a connection forgrounding said sleeve.

3. An antenna in accordance with claim 2,4

half wavelength section, and asleeve one-half wavelength longsurrounding said last section and supported therefrom only at itsmid-point for preventing radiation therefrom, and a connection an oddmultiple of a half wavelengthV long grounding said sleeve. I

6. An antenna for obtaining moderately great vertical directivity andlittle or no'horizontal-f directivity, comprising a vertical rod, -highfrequency apparatus connected to the lower end of said rod, anadjustable sleeve, at the extreme top end of said rod for adjusting thelength thereof, a sleeve surrounding each alternate half wavelengthsection of saidv rod and insulated therefrom, and a .connection an oddmultiple of a halfy wave longconneoting each of said last sleeves andground for preventing radiation from the 'surrounded"fsecfftionvs 7. Anantenna in accordance with claim 16,

characterized in A`this that said rod is altube whose t outer diameteris anvappreciable fraction ofahalf wave long, and' said'connections'.extend within said tube from said sleeves togroundi 8. Anantennal in accordance with 'claim` 6,'v characterized in this.that-said antenna'is mounted on the topfoii abuilding, the lcwermostpor- Y tion of said antenna beingy set below the roof top forapproximately o'rie-ciui'trtery wavelength, said Isurface of saidsupportvffor d mately, one-quarterathejflength' of the operating yportion o! the antenna above said roof top being a multiple of a halfwave, said roof being ot high conductivity and maintained at `zero radiofrequency potential.

9. An antenna in accordance with claim 6, characterized in this thatsaid antenna is mounted on the top of a building, the lcwermost portionof said antenna being set below the roof top for approximatelyone-quarter wavelength, said portion of the antenna above said roof topbeing a multiple-of a half wave, said high frequency apparatus beingcoupled to said antenna at the portion below said roof top, said rooftop being of high conductivity and grounded.

10. An antenna comprising two lhalf wavelength radiating sectionsseparated by another half wavelength section, a sleeve one-half wavelength long surrounding said last section and insulated therefrom forpreventing radiation therefrom, and a connection grounding said sleeve.

11. An lantenna for obtaining moderately great vertical directivity andlittle or no horizontal directivity, comprising a vertical rod, highfrequency apparatus connected to the lower end of said rod, a sleevesurrounding each alternate half wavelength section of said rod, theportions of said sleeve on both sides of the center being insulated fromthe rod, and a connection a multiple of a half wave long connectingeach' of said sleeves to ground for preventing radiation from thesurrounding sections.

12. An antennal comprising a substantially straight hollow rod,alternate half wave sections of which radiate, means for preventingradiation from each half wave section located between radiating sectionscomprising a sleeve surrounding said section, and a connection insidesaid rod groundngsaid sleeve.

13. An antenna comprising a substantially straight hollow rod, alternatehalf wave sections of which radiate, means for preventing radiation fromeach half .wave section located between radiating sections comprising asleeve surrounding said section, and aconnection inside said rod Y andinsulatingly positioned wth respect thereto straight., hollowrod-,-,alternate lhalf wave sectionscf which radiatemeans for preventingradiation-from each half 'wave section located bef tween radiatingsectionseomprising a sleeve surrorundingsaid` section, and fa'connection inside saidl rod-groundingsaid' `slee've,`.j.said connectionbeingra, multiple o'ft'half the length of the' operat.`

ing-Wave. u ,f

15.* An antenna vcomprising a substantially vvertical hollowrod,alternate vhalf wave sections of which radiate,saidyrodubeingmounted ona grounded'support 'andbein'g below the upper distance approxiwave,said'portionhaboveisaid support being a multiple 'of half :the operatingwave, means for preventing radiationi'rom' each half wave section ofsaidfrod located between radiating sections ,c'omprising'ashieldsurro'unding said section, av connection inside said rodgrounding said wsliieldr' and high frequency apparatus coupled .tosaidrod atfthe portion below the upper surface of said' support.: e

CLARENCE W. HANSELL.

